diff --git a/Project.toml b/Project.toml
index de33516..2f2c697 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,20 +1,24 @@
 name = "BlockDiagonals"
 uuid = "0a1fb500-61f7-11e9-3c65-f5ef3456f9f0"
 authors = ["Invenia Technical Computing Corporation"]
-version = "0.1.6"
+version = "0.1.7"
 
 [deps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
 [compat]
-FillArrays = "0.6, 0.7, 0.8"
+ChainRulesCore = "0.9"
+FillArrays = "0.6, 0.7, 0.8, 0.9, 0.10"
 julia = "1"
 
 [extras]
+ChainRulesTestUtils = "cdddcdb0-9152-4a09-a978-84456f9df70a"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+FiniteDifferences = "26cc04aa-876d-5657-8c51-4c34ba976000"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Documenter", "Random", "Test"]
+test = ["ChainRulesTestUtils", "Documenter", "FiniteDifferences", "Random", "Test"]
diff --git a/src/BlockDiagonals.jl b/src/BlockDiagonals.jl
index b6af37e..1d5aaf4 100644
--- a/src/BlockDiagonals.jl
+++ b/src/BlockDiagonals.jl
@@ -1,6 +1,7 @@
 module BlockDiagonals
 
 using Base: @propagate_inbounds
+using ChainRulesCore
 using FillArrays: Zeros
 using LinearAlgebra
 
diff --git a/src/blockdiagonal.jl b/src/blockdiagonal.jl
index c1dc34d..99301c7 100644
--- a/src/blockdiagonal.jl
+++ b/src/blockdiagonal.jl
@@ -17,6 +17,11 @@ function BlockDiagonal(blocks::Vector{V}) where {T, V<:AbstractMatrix{T}}
     return BlockDiagonal{T, V}(blocks)
 end
 
+function ChainRulesCore.rrule(::Type{<:BlockDiagonal}, blocks::Vector{V}) where {V}
+    BlockDiagonal_pullback(Δ::Composite) = (NO_FIELDS, Δ.blocks)
+    return BlockDiagonal(blocks), BlockDiagonal_pullback
+end
+
 BlockDiagonal(B::BlockDiagonal) = B
 
 is_square(A::AbstractMatrix) = size(A, 1) == size(A, 2)
@@ -102,6 +107,24 @@ end
 
 ## Base
 Base.Matrix(B::BlockDiagonal) = cat(blocks(B)...; dims=(1, 2))
+
+function ChainRulesCore.rrule(::Type{<:Base.Matrix}, B::T) where {T<:BlockDiagonal}
+    nrows = size.(B.blocks, 1)
+    ncols = size.(B.blocks, 2)
+    function Matrix_pullback(Δ::Matrix)
+        row_idxs = cumsum(nrows) .- nrows .+ 1
+        col_idxs = cumsum(ncols) .- ncols .+ 1
+
+        Δblocks = map(eachindex(nrows)) do n
+            block_rows = row_idxs[n]:(row_idxs[n] + nrows[n] - 1)
+            block_cols = col_idxs[n]:(col_idxs[n] + ncols[n] - 1)
+            return Δ[block_rows, block_cols] 
+        end
+        return (NO_FIELDS, Composite{T}(blocks=Δblocks))
+    end
+    return Matrix(B), Matrix_pullback
+end
+
 Base.size(B::BlockDiagonal) = sum(first∘size, blocks(B)), sum(last∘size, blocks(B))
 Base.similar(B::BlockDiagonal) = BlockDiagonal(map(similar, blocks(B)))
 Base.parent(B::BlockDiagonal) = B.blocks
diff --git a/test/blockdiagonal.jl b/test/blockdiagonal.jl
index 966f626..8a67c5e 100644
--- a/test/blockdiagonal.jl
+++ b/test/blockdiagonal.jl
@@ -3,6 +3,16 @@ using BlockDiagonals: isequal_blocksizes
 using Random
 using Test
 
+function FiniteDifferences.to_vec(X::BlockDiagonal)
+    x, blocks_from_vec = to_vec(X.blocks)
+    BlockDiagonal_from_vec(x_vec) = BlockDiagonal(blocks_from_vec(x_vec))
+    return x, BlockDiagonal_from_vec
+end
+
+function Base.isapprox(C::Composite{<:BlockDiagonal}, D::BlockDiagonal; kwargs...)
+    return isapprox(C.blocks, D.blocks; kwargs...)
+end
+
 @testset "blockdiagonal.jl" begin
     rng = MersenneTwister(123456)
     N1, N2, N3 = 3, 4, 5
@@ -61,6 +71,21 @@ using Test
         end
     end  # AbstractArray
 
+    @testset "ChainRules" begin
+        @testset "BlockDiagonal" begin
+            x = [randn(1, 2), randn(2, 2)]
+            x̄ = [randn(1, 2), randn(2, 2)]
+            ȳ = Composite{typeof(BlockDiagonal(x))}(blocks=[randn(1, 2), randn(2, 2)])
+            rrule_test(BlockDiagonal, ȳ, (x, x̄))
+        end
+        @testset "Matrix" begin
+            D = BlockDiagonal([randn(1, 2), randn(2, 2)])
+            D̄ = Composite{typeof(D)}((blocks=[randn(1, 2), randn(2, 2)]), )
+            Ȳ = randn(size(D))
+            rrule_test(Matrix, Ȳ, (D, D̄))
+        end
+    end
+
     @testset "isequal_blocksizes" begin
         @test isequal_blocksizes(b1, b1) == true
         @test isequal_blocksizes(b1, similar(b1)) == true
diff --git a/test/runtests.jl b/test/runtests.jl
index 38a2cb3..8557958 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,5 +1,8 @@
 using BlockDiagonals
+using ChainRulesCore
+using ChainRulesTestUtils
 using Documenter
+using FiniteDifferences # For overloading to_vec
 using Test
 
 @testset "BlockDiagonals" begin